Asymmetrical excitation type magnetic device and method of manufacture thereof

ABSTRACT

An asymmetric excitation type magnetic device is provided with a composite magnetic body composed of a first magnetic layer having a relatively strong coercive force and a second magnetic layer having a relatively weak coercive force which layers are combined so as to have their respective magnetic anisotropy oriented in the same direction. To such a composite magnetic body are applied external positive and negative asymmetric magnetic fields in a specified order thereby to produce variations in magnetic flux due to an escpecially quick magnetization reversal and resultantly to generate steep pulse outputs across a detecting coil.

BACKGROUND OF THE INVENTION

The present invention relates to an asymmetrically exciting typemagnetic device made of composite magnetic materials capable ofgenerating a steep pulse electromotive force in response to the actionof an exterior magnetic field.

The exterior magnetic field can be produced by a permanent electromagnetor the magnetic field induced when an electric current flows.

Such electromagnetic type pulse generators are adapted to be used toproduce the pulse signals for the position of a moving body and can beapplied to electric and electronic apparatuses and automatic controlsystems all of which need a large number of successive pulse signals.

In addition, they can be used as an operation timing control device witha high accuracy for generating pulse signals for controlling variouscomputers in an automotive vehicle and ensuring an optimum ignitionoperation of a gasoline engine and an optimum heating or coolingoperation in response to the variations in gas pressure in a stirlingengine.

The present invention can be also used as an ampere meter and a currentsensor for detecting an overcurrent in an electric distribution system.

The electric current sensor can be used to detect not only the currentincluding a direct current which ranges from a super low frequency rangeto a high frequency range but also to measure an overcurrent such as animpulse.

The present invention further provides measuring instruments which canbe used in voltage meters and ampere meters.

Furthermore, the magnetic device in accordance with the presentinvention can be widely used as a special magnetic storage device forwriting and reading information under the action of an exterior magneticfield.

Various methods for producing pulses by utilizing electromagneticinduction have been used and demonstrated.

In general, the magnitude of the electromotive force produced by theelectromagnetic induction is dependent upon the variations in time ofthe magnetic flux intersecting a detection coil mounted on aferromagnetic material so that when the variation ratio becomesextremely low, no electromotive force is produced.

However, extensive studies and experiments have been conducted to findmagnetic materials, which are not dependent upon the ratio of variationsin time of the intersecting magnetic flux. For instance, according to aBistable Magnetic Device disclosed in U.S. Pat. No. 3,820,090 by J. R.Wiegand, a Self-Nucleating Magnetic Wire is produced by subjectingpermalloy to a tension and twisting process so that the coercive forceat the shell portion is stronger than that at the core portion. It has aphenomenon that when one exterior magnetic field disappears, a pulse isgenerated and that when the magnetic field disappears, the direction ofmagnetization of the core portion of the wire establishes a returnmagnetic path of the shell by self reversal. Therefore the underlyingprinciple of the above-mentioned wire is that in response to thevariations of the magnetic flux, a pulse is generated across a detectioncoil.

The above-described reversal phenomenon inevitably occurs when theexternal magnetic field disappears because in the case of a shortmagnetic body, the action of the opposite magnetic field at each pole isgenerally dominant. However, the output pulse thus produced isrelatively low and there is a defect that it is very difficult tocorrectly control a time point at which a pulse is generated.

So far, as means for indirectly measuring the value of a current flowingthrough a line, there has been used a method in which the magnetic fieldproduced when the current flows through the line is trapped by aninstrumental transformer utilizing iron cores, but this method has alsothe problem that the magnetic circuit and the winding cannot be madecompact in size and light in weight.

Furthermore, there has been proposed and used a method in which anelectric current is measured by a semiconductor element utilizing theHall effect and a magnetic circuit, but this method also has the problemthat the temperature characteristic and stable operation cannot beensured so that this method is not reliable in operation.

The utilization of composite magnets especially as a current sensor hasbeen proposed and demonstrated, but this method has the problems thatthe detection capability is remarkably varied depending upon themagnetization history, i.e. how the composite magnetic body used waspreviously magnetized. This is an inevitable phenomenon depending uponthe magnetic hysteresis so that when used as an electric current sensor,it must be provided with some suitable correction means.

On the other hand, according to the present invention, an asymmetricexcitation type composite magnetic body is used so that various objectsof the present invention can be attained by a simple means.

An ignition device in accordance with the present invention can be usednot only in a conventional contact type ignition system but also anon-contact ignition system which has been developed recently.

At present, there are known electromagnetic type pickups for generatingpulse signals equal to the number of the gear shaped magnetic poles perrotation of the rotating shaft of a distributor.

In this case, when the diameter of the gear-shaped magnetic pole is, forinstance, of the order of 30 mm, the upper limit of the angle ofrotation for generating one pulse is of the order of from 10° to 15° sothat there has been a strong demand for a pulse generator capable ofgenerating pulses at a high degree of resolution of the order of 1° orless.

Furthermore, the conventional ignition systems need at least two kindsof signals each representative of the angle of rotation of thecrankshaft.

More particularly, one kind of pulse is needed to control the angle ofrotation of the above-mentioned distributor while the other kind ofpulse is needed to detect which cylinder is operated or ignited.

In order to generate such two kinds of pulse signals, two signalgenerators are mounted and must be spaced apart from each other by asuitable distance to prevent mutual electromagnetic inductioninterference. It follows therefore that the whole volume of the twosignal generators inevitably becomes large so that there has been also ademand for signal generators compact in size and light in weight or justone generator capable of accomplishing the functions of two signalgenerators.

Furthermore, in the case of the storage devices utilizing theconventional magnetic bodies, in order to increase the output voltagederived on the read-out operation, means for increasing the ratio ofvariations of the intersecting magnetic flux have been provided. As aresult, there exist the problems that the electric current forgenerating the magnetic field must be shaped in the form of arectangular waveform and that the magnetic body must be rotated at ahigh speed.

SUMMARY OF THE INVENTION

In view of the above, a first object of the present invention is toprovide a method for the production of a composite magnetic body whichis subjected to a special treatment and which operates in anasymmetrical excitation mode, and a magnetic device utilizing thespecific characteristics of such composite magnetic body.

More particularly the present invention is to provide a method fortwisting a special ferromagnetic wire as a method for the production ofcomposite magnetic bodies having special characteristics due toasymmetrical excitation.

A second object of the present invention is to provide an asymmetricallyexciting type magnetic device in which a horizontal magnetic layer and avertical magnetic layer are composed of a composite magnetic bodycomposed of different kinds of ferromagnetic molecules withoutsubjecting a ferromagnetic body to mechanical methods such as tension,twisting and other methods, whereby high-quality pulse electromotiveforces are produced by an asymmetric exciting magnetic method.

A third object of the present invention is to provide a novel sensormeans capable of quickly and simply measuring the magnitude of anelectric current ranging from an extremely small current to a strongcurrent or an overcurrent.

A fourth object of the present invention is to provide a magnetic devicein which a plurality of composite magnetic bodies are arranged and anasymmetrical special magnetic field is sequentially applied to them sothat, for instance, even when a magnet is displaced at an extremelysmall velocity, pulses are successively generated.

A fifth object of the present invention is to provide an electromagnetictype pulse generator adapted to detect a position and an angle ofrotation of various mechanical devices by applying the capability ofdetecting the position of the composite magnetic body from among a largenumber of composite magnetic bodies which contributes to the generationof a pulse.

A sixth object of the present invention is to provide an ignition timingcontrol device in which a rotating pulse generator capable of generatingsimultaneously a signal for sensing the angle of rotation of acrankshaft and a signal for sensing a cylinder in the ignition system ofa gasoline engine with a high degree of accuracy, whereby an optimumcontrol can be attained by cooperating said pulses with a control signalfor a computer mounted on an automotive vehicle.

A seventh object of the present invention is to provide high-performancestationary type and movable type storage devices which operateindependently of the variation rates of the intersecting magnetic fluxon reading-out information from a magnetic storage device.

The above and other objects, effects and features of the presentinvention will become more apparent from the following description ofpreferred embodiments thereof taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 3 are schematic views illustrating an embodiment of a pulsegenerator utilizing an asymmetric excitation type magnetic device inaccordance with the present invention;

FIG. 2 is a view used to explain the underlying principle of anasymmetrical excitation type magnetic device;

FIGS. 4-6 are sectional views illustrating an embodiment of anasymmetric excitation type magnetic device;

FIG. 7 is a schematic view of another embodiment thereof;

FIGS. 8, 10 and 11 show an embodiment of a current ammeter in accordancewith the present invention;

FIGS. 9(a) and 9(b) are a time chart used to explain the mode ofoperation thereof;

FIG. 12 is a circuit diagram of an ammeter utilizing a compositemagnetic body in accordance with the present invention;

FIG. 13 shows schematically a cylindrical coil;

FIG. 14 is a schematic view of an embodiment having a spiral conductor;

FIGS. 15(1-3) and 16(1, 2, 1A, 2A, 3 and 3A) show time charts,respectively, of an exerting magnetic field and pulse electromotiveforces;

FIGS. 17, 18 and 21 are schematic views illustrating an embodiment of anelectromagnetic type pulse generator in accordance with the presentinvention;

FIGS. 19(1-2), 20(1-3) and 22(1-3) show time charts of the exertedmagnetic field and the pulse electromotive force, respectively; and

FIG. 23 is a schematic view used to explain an embodiment of an ignitiontiming control device in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a system in which the exterior magnetic field is controlledby the electric current excitation. An asymmetric excitation typemagnetic device 1 has an exciting coil 2 through which flows an electriccurrent at a predetermined magnitude for producing an oriented magneticfield, an auxiliary magnetic field and a main magnetic field, and adetection coil 3 for inducing pulses.

For the sake of better understanding of the underlying principle of thepresent invention, the magnetic characteristics of the asymmetricexcitation type magnetic device 1 in accordance with the presentinvention will be described with reference to FIG. 2.

FIG. 2 shows a model of a composite magnetic layer consisting of alamination of two kinds of ferromagnetic molecules which have differentcoercive forces and are anisotropic in a surface of FIG. 2 and laminatedin such a way that anisotropy becomes coaxial.

More particularly, an asymmetric excitation type magnetic device 1 has alamination consisting of a first magnetic layer 4 having a relativelystrong coercive force and a second magnetic layer 5 having a relativelyweak coercive force which are deposited in such a way that both of theanisotropies of the first and second magnetic layer are coaxial withrespect to each other as indicated by white arrows and the device 1 hasthe following described magnetic characteristics when the exteriormagnetic field is caused to operate by the asymmetrical excitationmethod.

Previously a strong orientation magnetic field indicated by a blackarrow 6 is exerted so that the whole asymmetric excitation type device 1is first magnetized in the positive direction (in the right direction inFIG. 2) and then the magnetic field is removed.

Next a relatively weak auxiliary magnetic field 7 is applied so that aportion of the second magnetic layer 5 which has a weak coercive force;that is, only the portion indicated by a white arrow +5 m is displacedin the negative direction (in the left direction in FIG. 2) as indicatedby a white arrow -5 m.

In this case, the portion -5 m displaced in the negative direction hasuniaxial magnetic anisotropy so that it can be maintained in this stateeven after the auxiliary magnetic field 7 is removed.

Next when it is desired to displace the portion having a relatively weakcoercive force in the positive direction as indicated by the arrow +5 mby applying again the main magnetic field 8, the reversal displacementvelocity is extremely high because the displacement is made in the samedirection as the direction of the first magnetic layer 4 which ismagnetized and has a high coercive force.

It follows therefore that when the detection coil 3 is wound around theasymmetric excitation type magnetic device 1, a steep pulseelectromotive force can be induced due to the variation of the magneticflux caused by the sudden displacement.

In this case, the main magnetic field 8 may have also the function ofthe orientation magnetic field 6 so that the underlying principle of thepresent invention remains unchanged even when the device 1 is actuatedby the weak auxiliary magnetic field 7 and the strong main magneticfield 8.

So far the composite magnetic layer has been described as havinganisotropy in the surface of FIG. 2, but even when the asymmetricexcitation magnetic device in accordance with the present inventionconsists of the composite magnetic layer of the so-called verticallymagnetized film obtained by treating the anisotropic direction ofdifferent kinds of ferromagnetic molecules which have different coerciveforces so as to be perpendicular to the surface of FIG. 2, the samefunction and effects can be attained. In this case, it is apparent thatthe magnetic fields are applied in the vertical direction.

When the magnetic layers having anisotropy in the surface of FIG. 2sandwich the composite magnetic layer from both surfaces thereof, thelatter is very effective as it functions as an auxiliary magnet.

So far, in order to apply the external magnetic flux, it has beendescribed that the electric current is made to flow through the excitingcoil, but even when a permanent magnet is used instead of the externalmagnetic field, the mode of operation remains unchanged.

For instance, FIG. 3 shows that the detection coil 3 is wound around theasymmetric excitation type magnetic device 1 and an auxiliary magnet 9producing the above-mentioned auxiliary magnetic field is disposedadjacent to the magnetic device 1. In this arrangement, when the mainmagnet 10 is moved toward the magnetic device 1, it becomes possible toinduce a steep pulse electromotive force across the detection coil 3.

Next the examples of the practical methods for manufacturing theasymmetric excitation type magnetic devices 1 will be described.

FIG. 4 is a sectional view of the magnetic device in which two kinds offerromagnetic molecules having different compositions are sequentiallydeposited alternately in the form of a plane by a DC sputtering processwherein a high voltage of the order of a few kilovolts (KV) is appliedin the argon atmosphere of 3.0×10⁻² Torr.

In this case, the magnetic device 1 is produced in the DC magnetic fieldso that the magnetic anisotropic directions of each layer may be thesame.

Reference numeral 12 represents a first magnetic layer having acomposition (40 Fe--50 Co--10V) and a coercive force of 30 (Oe).

Reference numeral 13 designates a second magnetic layer with acomposition (46 Fe--44 Co--10V) and a coercive force 80 (Oe). Both ofthe first and second magnetic films have the same thickness of 0.5micrometers and are laminated one over another. The measurements of thecoercive forces were obtained from the upper and lower major surfaces ofthe magnetic device 1 by the magnetic-kur-effect process.

Next the magnetic device 1 thus produced was cut into a specimen 5 mm inwidth and 20 mm in length and a detection coil consisting of 100 turnswas wound around the specimen in the easy axis of magnetization thereof,thereby fabricating a pulse generator.

In order to apply the external magnetic field, the asymmetric excitationmethod has been adopted in which the orientation magnetic field, theauxiliary magnetic field and the main magnetic field were determined bythe movement of permanent magnet.

First the orientation magnetic field of 200 (Oe) was applied so that thewhole magnetic device is magnetized in the positive direction (forinstance, in the right direction). Thereafter, when the auxiliarymagnetic field of the order of 40 (Oe) was applied in the negativedirection (in the left direction), only the direction of magnetizationof the second magnetic layer was reversed and was maintinaed in thisstate as described hereinbefore. Next when the main magnetic field inthe positive direction exceeds 40 (Oe), the quick reversal of the secondmagnetic layer was effected. As a result, a steep pulse electromotiveforce of 30 mV with a higher degree of S/N ratio was induced across thedetection coil.

Furthermore, as one of the methods for the production of asymmetricexcitation type magnetic devices, it is possible to produce a compositemagnetic layer consisting of first and second magnetic layers 12 and 13by repeating, over a short period of time, the conditions for growingthe two kinds of magnetic layers, that is, the first magnetic layer andthe second magnetic layer in the above-mentioned sputtering process.

Therefore, as shown in FIG. 5, formed over the major surface of asubstrate such as a glass or metal plate 14 was a flat magnetic filmwhich is one micrometer in thickness consisting of the mixedferromagnetic molecules, whereby the asymmetric excitation type magneticdevice 15 was obtained.

The detection coil was wound in a manner substantially similar to thatdescribed above and the external magnetic field was applied by theasymmetric excitation method, so that the pulse generation phenomenonsubstantially similar to that described above could be observed. Suchphenomenon can be produced in an asymmetric excitation magnetic deviceconsisting of a vertical magnetic film due to the same underlyingprinciple of the present invention.

FIG. 6 shows an asymmetric excitation type magnetic device which wasproduced by growing a first magnetic layer which consists of aferromagnetic substrate 16 in which anisotropic directions are orientedin the same direction, closely contacting a thin second magnetic layer17 different in kind or composition from the first magnetic layer 16over the major surface thereof, and rolling them into a uniformlamination.

FIG. 7 shows an embodiment in which first and second cylindricalmagnetic layers 19 and 20 are deposited over the cylindrical surface ofa core line 18 made of a non-magnetic material. In this case, twomagnetic layers are deposited over the cylindrical surface of the corewire, but it should be understood that even if more than three magneticlayers can be laminated, the above-described functions and effects canbe similarly attained.

In order to grow the ferromagnetic layers by depositing theferromagnetic molecules, in addition to the above-mentioned sputteringprocess, the vacuum evaporation process, the electric plating process,the non-electrolytic plating process and so on can be, of course, used.Furthermore, they can be produced by the rolling of leaf-shaped magneticfoils or the cylindrical cladding process.

Therefore, the asymmetric excitation type magnetic devices in accordancewith the present invention produced in the manners described above canbe made thin in thickness and compact in size in a simple manner so thatwhen the flat detection coil defined by the vacuum evaporation processor the printing process is used, the whole asymmetric excitation typemagnetic devices in accordance with the present invention can be madefurther compact in size.

When permalloy (Fe, Ni) was used as a component of the asymmetricexcitation type magnetic device in accordance with the presentinvention, the effects and features substantially similar to thosedescribed above can be attained. In addition, the present invention canuse amorphous magnetic materials or the ferromagnetic molecules of theoxidized magnetic materials to that the asymmetric excitation typemagnetic devices in various constructions and having various functionscan be produced.

Furthermore, when the ferromagnetic molecular layers in accordance withthe present invention are subjected to a heat-treatment, magneticcharacteristics can be imparted to the magnetic device or the latter canbe further stabilized.

The asymmetric excitation type magnetic device in accordance with thepresent invention is an excellent device capable of generatinghigh-quality pulse electromotive forces due to the unique application ofthe magnetic field or the asymmetric excitation method withoutsubjecting the component parts under the tension process, the twistingand untwisting process and other mechanical processes.

According to the present invention, the process of bonding in a coaxialdirection the anisotropy of different kinds of ferromagnetic moleculesin a horizontal or vertical plane is used so that the finished productscan be made considerably compact in size.

Therefore when not only a unitary pulse generator is designed andconstructed but also a magnetic-sensitive device comprising a pluralityof asymmetric excitation magnetic devices are arranged in a plane into aunitary construction as a magnetic-sensitive device and when themagnetic field of a magnet which moves straight, for instance, along theabove-mentioned magnetic-sensitive device, it becomes possible to detecta time when a pulse is generated, thereby designating the position of amachine or equipment mounted with a magnet. For instance, theabove-mentioned magnetic-sensitive device can be widely used for theautomation of various electric, electronic and mechanical machines andequipment each of which has a stationary portion and a moving portion.

Furthermore, when a plurality of asymmetric excitation type magneticdevices mounted on a cylindrical surface is used as a stator and alsoone or more magnets are used as a rotor, a rotating pulse generatorwhich is extremely compact in size can be obtained.

In addition, when the asymmetric excitation type magnetic device inaccordance with the present invention is divided into a plurality ofextremely small regions which are interconnected with excitation wiresin the form of a matrix and a unique magnetic field is applied to themby the above-mentioned asymmetric excitation method, there can beprovided a novel stationary storage device which is basically differentfrom the conventional disk memories which must be spun.

The present invention also relates to an ammeter of an asymmetricexcitation type provided by various special treatments.

First, the composite magnets used in the present invention will bebriefly described.

For instance, when a wire-shaped ferromagnetic material is, forinstance, subjected to external stresses or is twisted, it becomes acomposite magnet in which the portion adjacent the axis of the wire hasa relative high coercive force while the outer peripheral portionadjacent said first mentioned portion has a small coercive force. Suchcomposite magnets can be provided by laminating a plurality of magneticlayers each having different magnetic characteristics such as metaloxides, amorphous magnets and so on in such a way as to have uniaxialanisotropy. These composite magnets have the following specialcharacteristics.

First, only the direction of magnetization of the portion having arelatively low coercive force can be reversed to the positive ornegative direction in response to the direction of application of theexternal magnetic field by the asymmetric excitation due to the externalmagnetic field. Furthermore, the reversal speed is considerably high inthe direction of magnetization of the adjacent portion having a strongcoercive force.

Therefore, in response to the variations of magnetic flux due to suchfast reversal speed, it becomes possible to induce a steep pulse signalacross a detection coil disposed adjacent to the composite magnet.

It follows therefore that when the external magnetic field is composedof alternative positive and negative magnetic fields produced by analternating current, a time when a pulse signal is induced can bedetected thereby to detect an electric current at this detection time.

However, in the composite magnets of the type described above, ithappens that the magnitude of the external magnetic field, that is, thevalue of an alternating current does not become inevitably stablebecause it depends upon the previous history of how the portion having ahigh coercive force has been magnetized. This is an inevitablephenomenon due to a magnetic hysteresis characteristic so that when thecomposite magnets are used as an electric current sensor, some suitablecorrection means to correct or compensate such variations must beprovided.

On the other hand, according to the present invention, the objects of acurrent sensor can be attained by a simple means to be described below.More particularly, according to the present invention, a bias magneticfield having a predetermined relatively low value sufficient tomagnetize a portion having a low coercive force in the positivedirection, is normally applied and when the negative magnetic fieldproduced by an alternating current which intersects with theabove-mentioned bias magnetic field is greater than the bias field, apulse signal is induced across a sensor coil mounted on the compositemagnet at the next time when the positive magnetic field is produced.

Next a preferred embodiment of the present invention will be describedin detail with reference to the accompanying drawings.

FIG. 8 shows the fundamental construction and reference numeral 8-1represents the above-mentioned composite magnet; 8-2, a detection orsensor coil mounted on (for instance, wound around or disposed in thevicinity of) the composite magnet 8-1; 8-3, an exciting coil throughwhich an alternating current I flows to produce an external magneticfield; 8-4, a coil for producing a bias magnetic field in order toalways magnetize the portion having a low coercive force of thecomposite magnet 8-1 in the positive direction; and 8-5, a directcurrent source.

Next, the mode of operation will be described with reference to the timechart shown in FIG. 9. First, a constant bias magnetic field H_(DC) isalways applied to the composite material 8-1 in the positive directionas indicated by the broken lines d.

When the exterior magnetic field H_(AC) produced by the alternatingsensor current I flowing through the -sensor element 8-1.

However, as shown in FIG. 9(b), when the external magnetic field H_(AC)produced by the sensor current I (in this case, the absolute value ofits maximum peak value is greater than H_(DC)) is applied, the combinedmagnetic field (H_(DC) +H_(AC)) indicate..d by the solid line isapplied.

More particularly, first only the region having a small coercive forceis displaced in the negative direction by the negative magnetic fieldH_(R). It is subsequently displaced or reversed in the positivedirection by the succeeding application of the positive magnetic fieldHs. In this case, the small coerciveforce portion is reversed ordisplaced in the same positive direction of magnetization of theadjacent portion having a strong coercive force so that the displacementor reversal speed is very fast as described above.

As a result, at the time point at which a limit magnetic field H_(L)required for causing the displacement or reversal is applied, the steeppulse signal Vs is induced across the sensor coil 8-2 as shown in thelower portion of FIG. 9 so that it is confirmed by the detection of thispulse signal that a previously determined electric current flows.

In the above-described embodiment, DC is used to always apply apredetermined bias magnetic field, but as shown in FIG. 10 the sameeffect can be obtained when a permanent magnet 10-7 is disposed in thevicinity of the composite magnet 10-1.

In practice, when the current sensor in accordance with the presentinvention is disposed at the end of wiring, it becomes necessary tocheck whether or not the current sensor can correctly operate. In thiscase, for instance, as shown in FIG. 10, a permanent magnet 10-8 actingin the positive direction of the magnetic field is disposed and aclosed-magnetic-path auxiliary magnet 9 (indicated by the hatched lines)which is caused to normally be in contact with the permanent magnet 10-8is moved away therefrom by an operating member (or a push button or thelike). In this case, the positive magnetic field of the permanent magnet10-8 is applied so that the pulse signal Vs is induced. Consequently, inresponse to the detection of pulse signal Vs thus induced, the normaloperation of the ammeter can be confirmed. Alternatively, a checkauxiliary excitation coil (not shown) can be disposed through which anelectric current is caused to flow by a remote control system to producea magnetic field.

In the case of the application of the current sensor in accordance withthe present invention to a wiring system such as a power cable 11-11 asshown in FIG. 11 or other devices through which flows an electriccurrent having a high value, the current sensor is connected through aterminal 11-12 in a power board and a secondary current i is caused toflow through an exciting coil 11-14 wound around the core 11-13 of acurrent transformer. Thereafter following the above-described procedure,the composite magnet 11-1 is magnetized. Reference character r indicatesa resistor for adjusting the value of the exciting current.

In this case, it is so arranged that in response to the limited value ofthe current flowing through, for instance, the power cable 11-11, thepulse signal Vs is induced across the detection coil 2. Therefore, it isapparent that the operation and effects of a current sensor can beobtained.

Accordingly, in the cases of the above-described embodiments, when adetection current having a predetermined value is set so as tocorrespond to a limited current flowing through a line, the currentsensor in accordance with the present invention can be used as anovercurrent sensor with an extremely high accuracy.

As described above, the current sensor in accordance with the presentinvention can be made simple in construction and compact in size and candetermine a limited current in a suitable manner, and can operate withan extremely high accuracy. In addition, the current sensors inaccordance with the present invention can be produced at less cost andhave the effect to be applied as sensors for sensing various loadsconnected to the ends of a plurality of wiring systems.

Therefore, the pulse signals derived from the sensors disposed so as todetect a plurality of loads distributed over a large area are convertedinto optical signals so that the centralized monitor control can becarried out by constructing an optical cable network and furthermore thepresent invention may be equally applied to attain various effects.

Next, a circuit for detecting whether or not the current sensor inaccordance with the present invention normally operates correctly, willbe described hereunder.

Referring first to the accompanying drawings, the underlying principleof the present invention will be described.

FIG. 12 is a circuit diagram of a fundamental circuit in accordance withthe present invention. Reference numeral 12-1 designates a compositemagnet; 12-2, a detection coil mounted on (for instance, wound around ordisposed in the vicinity of) the composite magnet; 12-3, an excitingcoil adapted to produce a magnetic field which is dependent upon themagnitude of an alternating detection current I_(A) ; 12-4, a detectioncoil and 12-5, a switching means all of which are assembled into aunitary construction which in turn is disposed within a housing.

The special characteristics of the composite magnet 12-1 used in thepresent invention will be first described as follows.

When the positive and negative magnetic fields are produced by the AC asthe external magnetic fields intersect each other, it now becomespossible to detect the value of the AC in response to a time point whena pulse electromotive force is produced.

However, in addition to the above-described ferromagnetic bodies, itdoes not necessarily follow that the magnitude of the external magneticfield at a time when the pulse electromotive force is produced, that is,the value of the alternating current, is maintained at a constantmagnitude because it depends upon the history of how the portion havingthe large coercive force is magnetized even in the case of the compositemagnet used in the present invention.

However, in the current sensor in accordance with the present invention,the detection magnetic field is superposed at a predetermined timing ateach cycle of the alternating detecting current, that is, a limitmagnetic field having a magnitude sufficient to magnetize only theportion having a weak coercive force of the composite magnet in thepositive direction is applied at each cycle, so that the above-describedhistory is corrected and consequently the stable operation can beensured.

Furthermore, as shown in FIG. 13, the excitation coil 12-3 of FIG. 12which produces the magnetic field whose value is dependent upon themagnitude of the alternating detection current I_(A), is so designed andconstructed that the electric current flows from one terminal 13-12 tothe other terminal 13-12a of a cylindrical coil 13-11 formed by windinga sheet of conductor 13-10 and, as a result, a uniform magnetic fieldthus generated is caused to intersect the composite magnet 12-1 at ahollow portion of the cylindrical coil. The fact that the thickness ofthe front end of the plate of the conductor 13-10 is varied to adjust anelectric current density, whereby the magnetic field is uniformlyextended between the both ends of the cylinrical coil 13-11, isextremely effective to operate the composite magnet in accordance withthe present invention with a high accuracy.

Alternatively, as shown in FIG. 14, the arrangement in which an electriccurrent is caused to flow through a spiral coil 14-14 is effective.

Next, the role of the detecting coil 12-4 and an electric sensor inaccordance with the present invention will be described.

FIG. 15 shows an embodiment of a method for measuring the value of analternating detecting current I_(A) by utilizing the electric sensor inaccordance with the present invention. FIG. 15(1) shows a time chartwhen an exciting magnetic field H_(A) produced in the hollow portion ofthe cylindrical exciting coil, the bias magnetic fields H_(R1-R4) in thenegative direction which are gradually increased stepwise at each cycleand the detecting magnetic field +Hv having a limit value Hp in thepositive direction sufficient to reverse the direction of themagnetization of the portion of the composite magnet having a relativelylow coercive force are intersected by each other. Furthermore, a valueH_(F) is a limit value at which the direction of the magnetization ofthe portion of the composite magnet 1 having a relatively small coerciveforce is sufficiently reversed in the negative direction.

FIG. 15(2) shows the waveform of the magnetic fields combined in themanner described above. It is seen that the combined field of -(H_(A)-H_(R3)) acts on the composite magnet 1 as the auxiliary externalmagnetic field (corresponding to the above-mentioned H_(F)) in thenegative direction so that, as shown in FIG. 15(3), a small negativepulse E_(S1) is produced. On the other hand, when the main combinedmagnetic field +(H_(A) +H_(v)) acts in the positive direction, a steeppulse electromotive force Es is induced.

Therefore, since H_(F) represents a constant inherent to a compositemagnet and H_(R3) is a known detecting magnetic field which detects atime point at which a pulse is induced, the value of the detectedcurrent I_(A) can be obtained from the following equations:

    H.sub.A =H.sub.F -H.sub.R3

Hence,

    I.sub.A =N×H.sub.A

where N represents a number of turns of the coil through which flows thedetected current.

FIG. 16 shows an embodiment in which the above-described current sensoris used as an overcurrent sensor.

In this case, as shown in FIG. 16, the, detecting magnetic fields +Hvand -Hv each respectively correspond to the above-mentioned limitmagnetic fields Hp and H_(F) of the composite magnet at least everyother cycle of the detected current. During this interval, theelectromagnetic field H_(R) in the negative direction and theelectromagnetic field Hv in the positive direction are applied as a partof the detecting magnetic field in order to generate a predeterminedovercurrent.

The left portions of FIG. 16(1)-(3) shows the charts, respectively, ofthe magnetic fields and the pulse electromotive force E in the casewhere the value of an alternating current to be detected is within apredetermined range. More particularly, FIG. 16(1) shows the mode ofoperation of the detecting magnetic fields +Hv and -Hv whose valuescorrespond to those of the above-mentioned limit magnetic fields Hp andH_(F) of the composite magnet and the exciting magnetic field H_(A)produced by an alternating current to be detected in addition to themagnetic field H_(R) in the negative direction.

FIG. 16(2) shows the combined magnetic field so that, as shown in FIG.16(3), the electromotive force Ev₁ and Ev only are intermittentlygenerated at every other cycle in response to the positive and negativedetecting magnetic fields. Whether or not the current sensor inaccordance with the present invention is operating correctly can bedetected by the detection of the intermittent generation of the pulseelectromotive forces.

At the instant when the current to be detected reaches a predeterminedovercurrent, the mode of operation becomes as shown on the right sidesof FIGS. 16(1A)-(3A).

More particularly, FIG. 16(1A) shows the actions of the detectingmagnetic fields +Hv and -Hv and the magnetic field H_(R) on the excitingcurrent H_(A1) produced by an alternating current to be detected whichreaches a predetermined overcurrent.

As shown in FIG. 16(2A), in each cycle, after the magnetization of themagnetic field in the negative direction (which functions as theabove-mentioned auxiliary magnetic field) which is greater than thenegative limit magnetic field H_(F), the mode of magnetization of themagnetic field (which functions as the above-mentioned main magneticfield) in excess of the positive limit magnetic field Hp follows.

Therefore, as is shown in FIG. 16(3), the pulse electromotive forces Ev₁and Ev or Es₁ and Es are generated at each cycle due to the positive andnegative detecting magnetic fields so that the overcurrent condition canbe detected by the detection of the conditions of such succeedingpulses.

As described above, in the current sensor in accordance with the presentinvention, the detection of an electric current is carried out inresponse to the satisfactory or unsatisfactory conditions of thepulse-electromotive-force generation so that the detected pulse can becompletely separated from the pulses generated by the noise-likeelectromagnetic fields and detected.

For instance, in the case of the overcurrent sensor described above withreference to FIG. 7, when abnormal magnetic fields which are produced byan oscillating transient current are superposed on the magnetic fieldH_(A) , produced by the current to be detected and also on the detectingmagnetic field Hv, some pulses each of which is generated at anincorrect timing are generated. It follows, therefore, that theovercurrent mode is detected at a time point when each pulseelectromotive force is generated at a correct timing.

In the above-mentioned embodiment, the system has been explained inwhich one positive or negative detecting magnetic field is superposed ateach half cycle of an electric current to be detected, but, as shown inFIG. 12, a plurality of detecting magnetic fields can be produced at asuitable timing by the signal current generator 12-16 or variouscombinations of various magnetic fields can be used in accordance withthe objects.

An arithmetic-logic unit 12-17 measures the value of a detectingmagnetic field in response to the voltage across the resistor R at atime point when a pulse electromotive force is generated across adetecting coil 12-2 thereby to operate the value of an electric currentto be measured in a manner substantially similar to that describedabove.

Furthermore, the number of turns of the detecting coil 12-3 is increasedor decreased by actuating the switching means 12-5 thereof so that thevalue of the detecting magnetic field can be varied as shown in FIG. 12.In this case, a detecting magnetic field is varied in the form of theresultant magnetic field with the magnetic field produced by an electriccurrent to be detected so that it becomes possible to provide anelectric current sensor of the type in which a limit value of adetecting electric current can be adjusted or switched.

Referring next to FIG. 14, another method for adjusting or switching alimit value of an electric current to be detected will be described. Asshown in FIG. 14, in order to vary the magnitude of the limit value of adetecting electric current, a ferro-magnetic body having a suitablelength is used as a ferromagnetic control means 14-18 which in turn ismoved toward or away from the composite magnet 14-1.

The current sensor in accordance with the present invention can be madesimple in construction and compact in size and can measure any value ofan electric current with a high accuracy without using an instrumentaltransformer such as a current transformer. Furthermore, the presentinvention has a feature that a pulse electromotive force is generatedwhen the value of the electric current to be detected reaches apreviously determined value so that it can be used as an electric sensornot only in a power distribution system but also in general electriccircuits. Therefore, the current sensor in accordance with the presentinvention is very effective when used as a digital ammeter or anovercurrent sensor.

In addition, the current sensors in accordance with the presentinvention can be produced at less cost and have the feature that theycan be used as sensors for the early detections of the failures of aplurality of various kinds of loads especially at the ends of wiringsystems.

Therefore, the pulse signals from the sensors capable of detecting aplurality of loads distributed over a wide range can be converted intooptical signals so that the centralized monitor control becomes possibleby constructing a network of optical fiber cables.

Next, the underlying principle as well as the construction of thepresent invention will be described when the latter is applied to anelectromagnetic type pulse generator.

FIG. 17 shows a magnetic sensor 17-3 in which a plurality of compositemagnets 17-1 to 17-n are disposed in parallel with each other and spacedapart from each other by a suitable distance and a first detecting coil17-2 is wound around the above-mentioned composite magnet array in thedirection perpendicular thereto in such a way that the detection coil17-2 seems to cover the array of composite magnets 17-1 and independentsecond detecting coils 17-6 and 17-7 are wound around, for example, thespecific composite magnets 17-1 and 17-5, respectively.

In this case, various patterns of a plurality of first detecting coils17-2 may be considered. For instance, independent coils are wound aroundeach of the composite magnets 17-1, . . . , 17-n and the ends of thedetecting coils of the adjacent composite magnets are electricallyconnected in parallel or in series, thereby to define a sole firstdetecting coil. In addition, a plurality of composite magnets arrangedin the manner described above are regarded as warps, while conductorsfor defining a coil are regarded as wefts so that they are interwovenand their ends are electrically interconnected with each other, therebyalso defining a sole first detecting coil.

Referring still to FIG. 17, a first orientation magnet Mo is moved fromthe position shown in FIG. 17 in the right direction toward thecomposite magnet 17-1 as indicated by an arrow so that the compositemagnet is magnetized in the positive direction. Thereafter an auxiliarymagnet Ma is displaced in the right direction so that only a portionhaving a relatively low coercive force of the composite magnet isreversed in the negative direction.

Next, when a main magnet Mm is displaced in the right direction, eachcomposite magnet successively applied with the magnetic field of themain magnet Mm has its portion having a relative low coercive force themagnetization of which is reversed quickly. As a result, the steep pulseelectromotive forces are successively induced across the first detectingcoil 17-2.

In this case, the pulse electromotive force is induced across the seconddetecting coil 17-6 or 17-7 so that the passing position of the mainmagnet Mm can be detected and the pulse thus obtained is utilized as asignal for controlling a second control means.

The above-described effects and features can be similarly obtained evenwhen the magnetic sensor 17-3 is in the form of a cylinder and themagnets are rotated inside of the cylindrical sensor 17-3. In this case,a pulse generator capable of determining the angle of rotation can beprovided.

Referring next to FIG. 18, a plurality of composite magnets are arrangedaround the cylindrical surface of a cylinder 18-13 and are spaced apartfrom each other by a suitable distance. Further, a solenoid-shaped firstdetecting coil 18-14 is wound around the array of the composite magnets18-1 while independent second detecting coils 18-6 and 18-7 are woundaround the specific composite magnets 18-1 and 18-5, whereby a stator18-15 of the magnetic sensor is formed.

Next, an orientation magnet Mo, an auxiliary magnet Ma and a main magnetMm which revolve along the inner cylindrical surface of the stator 18-15are mounted on a rotating shaft 18-16 in such a way that the upper endsof the orientation, auxiliary and main magnets Mo, Ma and Mm become a Npole, a S pole and a N pole, respectively, whereby a rotor 18-17 isprovided.

The pulse generation principle of such rotating pulse generator issubstantially similar to that described above with reference to FIG. 17,but the modes of operation of the magnetic sensors described above withreference to FIG. 18 are apparent from the time charts shown in FIGS. 19and 20, respectively.

FIG. 19(1) shows the variations in time of the acting magnet when onecomposite magnet is observed. Ho represents the orientation magneticfield; Ha, the auxiliary magnetic field; and Mm, the main magneticfield.

When these magnetic fields intersect each other, a pulse is inducedacross the first detection coil 18-14 as shown in FIG. 19(2).

In terms of the variations in time of the pulses generated across thefirst detection coil 18-14, as shown in FIG. 20(1), whenever the mainmagnetic field Hm intersects a number of n composite magnets, the pulseelectromotive forces Vs are successively generated. The pulses generatedacross the second detecting coils 18-6 and 18-7 independently of eachother are shown as Vd6 in FIG. 20(2) and as Vd7 in FIG. 20(3).

The position of each detecting coil is previously determined so that itbecomes possible to detect by which composite magnet is generated eachpulse of a pulse train across the first detecting coil or it becomespossible to detect the angle of rotation of the rotor with a highaccuracy at the time when the pulse is generated. Concurrently, thepulse signal generated across the second detecting coil can be used as asignal to be applied to other controlled objects at the time when thepulse is generated.

So far, the mode of operation and effects of the rotor 18-17 having oneset consisting of three kinds of magnets have been described, but it isto be understood that when the magnet set is increased in number, thenumber of generated pulses can be increased accordingly.

According to the present invention, several means can be used as asystem for generating pulses by the action of one or more magnets. Forinstance, a rotating pulse generator as shown in FIG. 21 can alsogenerate pulses in a stable manner.

In the cylindrical magnetic sensor in which a plurality of compositemagnets are arranged at the outer cylindrical surface of a cylinder21-13 in parallel with the axis thereof and are angularly spaced apartfrom each other by a predetermined angle and a first detecting coil anda second detecting coil are wound around the composite magnets, acylindrical auxiliary magnet Ma whose top is a S pole is fitted over thecylindrical array of composite magnets disposed in the manner describedabove, thereby providing a stator. A rotor having at least one mainmagnet Mm (which may also function as an orientation magnet) whose topis a N pole is disposed within the cylinder 21-13 in such a way that itmay revolve along the inner cylindrical surface thereof.

In this case, the mode of operation of the magnetic fields acting on onecomposite magnet is shown in FIG. 22 and FIG. 22(1) shows the mainmagnetic field Ha produced by the auxiliary magnet Ma and the mainmagnetic field Hm produced by the revolving main magnet Mm and thecombined magnetic field of such fields is shown in FIG. 22(2).Therefore, as shown in FIG. 22(3), the pulse electromotive forces aregenerated whenever the main magnetic field Hm intersects the compositemagnets. And it is apparent that the second detecting coil generates apredetermined pulse signal in a manner substantially similar to thatdescribed above.

In FIG. 21, the cylindrical auxiliary magnet Ma is mounted over themagnetic sensor, but it is understood that it may be mounted in themagnetic sensor and that the present invention is not limited to anauxiliary magnet in the form of a cylinder and can equally utilize anauxiliary magnet Ma in any form as far as its magnetic flux effectivelyacts.

And as to the shape of each of a plurality of magnets constituting arotor, normal operation can be ensured even when the magnets used are inthe form of a cylinder or a rectangular prism. However, when anextremely high resolution is required in case of finding a position oran angle of rotation, for instance, a bar magnet is shaped in the formof a U so as to cause the magnetic lines to act on a composite magnet inthe vertical direction or a magnet whose edge portion is in opposingrelationship with respective composite magnets of the magnetic array isalso used so that the intensity of the magnetic field is applied in anacute angle. Alternatively, a magnet keeper made of a ferromagneticmaterial can be disposed along each composite magnet so that themagnetic field may intersect the composite magnet at an acute angle.

For instance, when a magnetic field which moves linearly is applied tothe whole array of a plurality of composite magnets disposed in a plane,a train of successive pulse outputs can be generated across the firstdetecting coil.

Furthermore, when predetermined specific composite magnets are woundwith the second detecting coils independently of each other, theinventor has succeeded in controlling other controlled objects inresponse to a pulse signal at a specific position simultaneous with thegeneration of the successive pulse signals whose positions can bedesignated. The above-described embodiment can be widely used inpractice in order to attain automation of various electric andelectronic devices and equipment and mechanical machines all of whichhave a stationary portion and a moving portion.

Usefulness of the rotating pulse generator in accordance with thepresent invention in which the stator is in the form of the cylindricalmagnetic sensor while one or more magnets constitute the rotor isconsiderably increased because, as described above in detail, while thefirst detecting coil generates successive pulses each designating anangle of rotation of the rotor, a pulse which is used as a coactingcontrol signal is generated with an extremely high accuracy and also anextremely high resolution can be obtained.

Especially, in the case of gasoline engines, in order to obtain anoptimum ignition timing, not only a pulse signal for controlling theangle of rotation of a distributor, but also a signal for detecting acylinder in which the combustion mixture is ignited are needed.Therefore, at present, two pulse generators are disposed and spacedapart from each other by a suitable distance in order to preventelectromagnetic induction interference and the like, but according tothe present invention, only one pulse generator is required and it isexpected that the rotating pulse generator in accordance with thepresent invention can be made more compact in size, light in weight andmore reliable in operation.

Furthermore, in accordance with the present invention, the pulseinformation representative of the conditions of the rotating parts whichrotate at from a high speed to an extremely slow speed can be obtained,and also the pulse information even in the case of an extremely slowspeed hitherto unattainable by the conventional pulse generators can besurely obtained.

Furthermore, in the case of the system in which the auxiliary magnet issecurely disposed to normally act, in order to cancel the auxiliarymagnetic field so as to permit the action of the strong main magneticfield, it is required to use a stronger main magnet. However, inpractice, when the magnitude of the main magnetic field is increased tosome extent, the effect that the operation is almost not adverselyaffected by disturbance of the exterior magnetic fields is attained sothat the present invention has a further advantage that the stableoperation can be ensured.

Furthermore, the pulse signals generated in accordance with the presentinvention can be applied to cooperate with a microcomputer or the likemounted on a vehicle so that the exchange of various operationinformation between the vehicle and the exterior can be effected.

Moreover, the present invention has an extremely considerable effectbecause the pulse generator in accordance with the present invention canbe made compact in size, light in weight, highly reliable in operation,can exhibit a high degree of performance and can be produced at lesscost all of which are very severe problems in the conventional pulsegenerators.

FIG. 23 is an embodiment of an ignition timing control device inaccordance with the present invention which is incorporated in acontact-less type ignition system including the rotating pulse generator23-20 of the type described above.

A first detecting coil 23-14 of the rotating pulse generator 23-20generates pulses for detecting an angle of rotation thereby to detect anangle of rotation of the rotor at a high resolution and a high accuracy.

The pulse is transmitted through an electronic circuit 23-21incorporating an ignitor to the gate of a semiconductor control element23-22 as a trigger pulse so that the control element 23-22 is turned on.A high-voltage thus generated across an ignition coil 23-23 isdistributed through a rotor 23-25 to a predetermined cylinder in whichan ignition is effected by a spark plug 23-26.

The rotating pulse generator 23-20 and the distributor 20-24 aredirectly interconnected with each other through the rotating shaft 23-16and are operatively connected to the crankshaft of an engine.Accordingly, the pulse generated across the second detecting coil 23-6or 23-7 for discriminating a cylinder can be simultaneously detected, sothat it becomes possible to discriminate with an extremely high accuracya cylinder in which a piston has reached the top dead point in thecompression stroke.

Furthermore, the pulse output generated by the rotating pulse generator23-20 is used, for instance, as a synchronizing signal in an electroniccontrol system. Recently, the computers and other control devices 23-26are mounted on a vehicle so that many control signals 23-27 whichindicate many timings in synchronism with the rotation of the enginewith a high accuracy are required. However, according to the device ofthe present invention, these signals can be derived from the pulsegenerator of the type described above in a simple manner.

Furthermore, a programmed control device 23-29 processes variousinformation signals 23-28 which are derived from various sensors,respectively, and represent various information such as the temperatureof water, the temperature of oil, the degree of humidity, the rotationalspeed, oscillations or vibrations and the like and these signals areprocessed by the programmed control device 23-29 so that the informationthus processed is applied to the electronic circuit 23-21 incorporatingan ignitor or to a microcomputer or is used in the feedback controlsystem, whereby the optimum controls can be obtained.

The effects and features of the above-described embodiments may besummarized as follows:

(1) Simple and Compact Construction:

In the cases of the conventional type ignition timing control device,two pulse generators are required for detecting an angle of rotation andfor discriminating a cylinder and must be spaced apart from each otherby a relatively long distance in order to prevent electromagneticinterference between them so that the conventional pulse generatorscannot be reduced in size. In accordance with the present invention, thesame objects described above can be attained by a single pulse generatorwhich is compact in size, light in weight and highly reliable inoperation when mounted on a vehicle.

(2) Improvement of Detection Accuracy:

As described in detail above, not only an angle of rotation can bedetected with a high accuracy and a high resolution by the pulses fordetecting an angle of rotation generated across a first detecting coiland furthermore a pulse for discriminating a cylinder can be generatedsimultaneously with the generation of the former pulses so that itbecomes possible to detect in which cylinder a piston has reached itstop dead center point in the compression stroke at an extremely highspeed and with a high accuracy.

Furthermore, as described above with reference to the conventionaldevices, the angle of rotation of the crankshaft of the engine has beendetected with a detection accuracy of 15° or 10° which is consideredunsatisfactory from the standpoint of the prevention of air pollutionand of performance so that there has been a strong demand for a noveltechnique capable of detecting the angle of rotation of the crankshaftat an extremely high accuracy of less than 1°.

In the revolving pulse generator in accordance with the presentinvention, a composite magnet which plays a very important role in thestator of cylindrical magnet sensor can be made in the form of a wire sothat it is expected to attain a high effect that when a plurality ofrotating pulse generators are disposed, a pulse generator which cangenerate pulses with a high resolution can be obtained.

In addition, in the case of a machine such as a recent Stering engineoperated in response to the variations in gas pressure due to alternateheating and cooling, the present invention can be effectively used forcontrolling an operating position.

(3) Increase Response Speed:

According to the present invention, the conditions of the rotating partsat from a high speed to an extremely low speed as in the case ofautomotive vehicles can be positively represented by pulse information.Therefore the effect capable of detecting the conditions at an extremelylow speed in the form of information pulses hitherto unattainable by theprior art is considerably useful.

(4) Resistance to Disturbance due to External

Magnetic Fields:

In the case of the system in which an auxiliary magnet is securelydisposed to normally act, a main magnetic field whose magnitude isenough to cancel the auxiliary magnetic field is required on generationof a pulse train. As a result, a strong main magnet must be used.However, in practice, it is effective that the operation can exhibit arelatively high resistance to the exterior magnetic field disturbancesand be maintained in a stable state even when a higher main magneticfield is applied.

(5) Others:

In general, the earlier the ignition timing in the engine is, the higherthe output becomes, but there is a problem that knocking occurs sometime and resultantly the engine performance decreases. Therefore, anoptimum ignition timing control is very important. In such a casedescribed above, the pulse signals generated by the rotating pulsegenerator having the magnetic sensor in accordance with the presentinvention are very effectively utilized.

In addition, as described before, the present invention has a furthereffect that information signals derived from various sensors mounted ona vehicle are processed and applied to the electronic circuit ormicrocomputer incorporating an ignitor or these signals are used in afeedback control system thereby ensuring an optimum operation control.Moreover, devices according to the present invention are operativelyconnected to other electronic circuits so that it has a yet furthereffect that the exchanges of various operation information within avehicle and the exterior thereof and control can be carried out, whichwas hitherto unattainable.

Furthermore, the present invention can attain the severe requirementsthat the devices must be compact in size and light in weight and can beproduced at less cost.

What is claimed is:
 1. An asymmetric excitation type magnetic devicehaving a composite magnetic body and a detecting coil, said compositemagnetic body being composed of a plurality of ferromagnetic moleculeswhich are different in composition and coercivity with respect to eachother and which are combined so as to have magnetic anisotropy orientedin the same direction, wherein external positive and negative asymmetricmagnetic fields are applied to said composite magnetic body in theorder: that first an auxiliary magnetic field is applied thereto so asto orient the direction of magnetization to a negative direction of onlythose ferromagnetic molecules in said composite magnetic body having arelatively small coercivity, and then next a main magnetic field isapplied thereto to reverse the direction of magnetization of saidferromagnetic molecules having a relatively small coercivity to apositive direction being the same as the direction of magnetization offerromagnetic molecules in said composite magnetic body having arelatively strong coercivity, thereby to produce variations in magneticflux in said composite magnetic body due to rapid flux reversal thereinfor thereby resultantly generating pulse outputs across said detectingcoil in response to said variations in magnetic flux.
 2. An asymmetricexcitation type magnetic device as set forth in claim 1, furthercomprising an exciting coil for causing a positive or negativeasymmetric external magnetic field to act upon the composite magneticbody by electric excitation, and a detecting coil for inducing adetecting pulse.
 3. An asymmetric excitation type magnetic device as setforth in claim 1, wherein the detecting coil is wound around saidcomposite magnetic body and said positive and negative external magneticfields are produced by permanent magnets.
 4. An asymmetric excitationtype magnetic device as set forth in claim 2 for use as a static storagedevice and in which said composite magnetic body is formed into at leastone composite magnetic layer having uniaxial anistropy and in which theferromagnetic molecules thereof having a relatively low coercivity aremagnetized in a negative direction under the action of an auxiliarymagnet, and in which the magnetization of said low coercivity moleculesis extremely quickly reversed to a positive direction the same as themagnetization direction of the ferromagnetic molecules thereof having ahigh coercivity under the action of a main magnet and which has aplurality of local positions distributed in said composite magneticlayer as storage points so that only when a plurality of first andsecond auxiliary magnetic fields are applied from the exterior to saidcomposite magnetic layer, a write action which reverses themagnetization of said composite magnetic layer to the negative directionby the combined magnetic field of said plurality of first and secondauxiliary magnetic fields is accomplished, and wherein a read-out actionby which a pulse is induced in said detecting coil is accomplished at atime point when the next magnetic field is applied to a predeterminedstorage point.
 5. An asymmetric excitation type magnetic device as setforth in claim 4, wherein said ferromagnetic molecules are arranged insuch a way that the uniaxial anisotropy thereof is in parallel with amajor surface of said composite magnetic body and a plurality ofconductors for producing said first auxiliary magnetic fields aredisposed in parallel with each other for each storage point of aplurality of storage points arranged in the form of a matrix so thatonly when the combined magnetic field of said first and second auxiliarymagnetic fields acts to cause a magnetization reversal at a storagepoint in the negative direction, a write action is effected; and whereina conductor for producing said main magnetic field is disposed at eachstorage position.
 6. An asymmetric excitation type magnetic device asset forth in claim 4 wherein the uniaxial anisotropy of each of saidferromagnetic molecules is made perpendicular to a major surface of saidcomposite magnetic layer and wherein exciting conductors for excitingsaid first and second auxiliary magnetic fields and said main magneticfield are arranged in a direction perpendicular to said major surface ofsaid composite magnetic layer and from at least one side thereof,whereby a write action or a read-out action may be accomplished.
 7. Anasymmetric excitation type magnetic device as set forth in claim 2 foruse as a moving type storage device wherein said composite magnetic bodycomprises a composite magnetic layer including a plurality offerromagnetic molecules each having uniaxial anisotropy and having aplurality of local points acting as information storage points therein,further comprising a magnetic head provided with exciting coils forproducing an auxiliary magnetic field and a main magnetic field,wherebywhen said composite magnetic layer is moved relative said magnetic head,a read-out action from each storage point at which information is storedis accomplished depending upon whether the magnetization of a portion ofsaid composite magnetic layer having a low coercivity was previouslyreversed to a negative direction or not.
 8. An asymmetric excitationtype magnetic device as set forth in claim 3, wherein a plurality ofsaid composite magnetic bodies each of which is so processed that only aportion thereof having a relatively low coercivity is magnetized in anegative direction under the force of an auxiliary magnet and isextremely quickly reversed in its magnetization to a positive directionwhich is the same as the direction of magnetization of a portion thereofhaving a high coercivity under the action of a main magnet, are arrangedin an array so as to be parallel with each other, and wherein a firstdetecting coil is wound around the array of said composite magneticbodies thus arrange, and wherein, of all said composite magnetic bodies,at least one selected composite magnetic body is wound with a seconddetecting coil independently, said device further comprising a pulsegenerator comprising an auxiliary magnet, a main magnet and anorientation magnet the magnetic fields of which auxiliary, main andorientation magnets are made to intersect said composite magnetic bodyarray, whereby pulse signals are generated across said first and seconddetecting coils.
 9. An asymmetric excitation type magnetic device as setforth in claim 8, wherein said auxiliary magnet is disposed in thevicinity of said composite magnetic body array such that the magneticfield produced by said auxiliary magnet normally acts upon saidcomposite magnetic body array, and wherein said main magnet and saidorientation magnet are so disposed as to move toward or away from saidcomposite magnetic body array.
 10. An asymmetric excitation typemagnetic device as set forth in claim 8, wherein a stator is providedcomposed of said plurality of said composite magnetic bodies which arearranged around an outer cylindrical surface of a cylinder in parallelwith the axis thereof and spaced apart form each other by apredetermined distance, a first detecting coil is wound around saidcomposite magnetic body array and a second detecting coil is woundaround at least one selected composite magnetic body of said compositemagnetic body array, independently, and wherein the magnetic fieldsproduced by said auxiliary magnet and a main magnet mounted on a rotorare applied to said stator, whereby pulse signals are derived by saidfirst and second detecting coils.
 11. An asymmetric excitation typemagnetic device as set forth in claim 10, wherein the magnetic fieldproduced by said auxiliary magnet arranged in the vicinity of saidcomposite magnetic body array always acts on said composite magneticbody array and a rotor mainly composed of said main magnet.
 12. Anasymmetric excitation type magnetic device as set forth in claim 8wherein a portion of said composite magnetic body having a relativelylow coercivity is magnetized in a negative direction under the action ofsaid auxiliary magnet and is extremely quickly reversed in itsmagnetization to a positive direction which is the same as the directionof magnetization of a portion of said composite magnetic body having ahigh coercivity under the action of said main magnet; and wherein aplurality of such composite magnetic bodies so formed are disposed in anarray in the form of a cylindrical surface of a cylinder, a firstdetecting coil is wound around said array of said composite magneticbodies thus arranged and, of said composite body array, at least oneselected composite magnetic body is wound with a second detecting coil,whereby a cylindrical magnet sensor is provided as a stator and wherebya rotating pulse generator is provided;wherein the magnetic fieldsproduced by said auxiliary magnet and said main magnet mounted on saidrotor are applied to said cylindrical composite magnetic body array, andwherein pulse signals generated across said first and second detectingcoils are made to cooperate with a control signal derived form anelectronic circuit incorporating an igniter, thereby providing anignition timing control device for an engine.
 13. A method for theproduction of an asymmetric excitation type magnetic device having acomposite magnetic body composed of a plurality of magnetic moleculeswhich are different in composition and coercivity with respect to eachother and which are combined so as to have magnetic anisotropy orientedin the same direction to generate a steep voltage pulse in response tomagnetization in the same direction, wherein a plurality offerromagnetic layers whose compositions are different from each otherare laminated over the surface of a substrate, thereby producing a flatcomposite magnetic layer.
 14. A method for the production of anasymmetric excitation type magnetic device having a composite magneticbody composed of a plurality of magnetic molecules which are differentin composition and coercivity with respect to each other and which arecombined so as to have magnetic anisotropy oriented in the samedirection, wherein a plurality of ferromagnetic molecules whosecompositions are different from each other are mixed and deposited overa surface of a substrate, thereby forming a flat composite magneticlayer.
 15. A method for the production of an asymmetric excitation typemagnetic device having a composite magnetic body composed of a pluralityof magnetic molecules which are different in composition and coercivitywith respect to each other and which are combined so as to have magneticanisotropy oriented in the same direction, wherein a plurality offerromagnetic molecules are deposited over the surface of a substrate insuch a way that each molecule has a magnetic anisotropy perpendicular tosaid surface of said substrate thereby to form a composite magneticlayer.
 16. A method for the production of an asymmetric excitationmagnetic device having a composite magnetic body composed of a pluralityof magnetic molecules which are different in composition and coercivitywith respect to each other and which are combined so as to have magneticanisotropy oriented in the same direction, wherein a plurality ofcylindrical ferromagnetic layers having a relatively high coercivity anda plurality of cylindrical ferromagnetic layers having a relatively lowcoercivity are formed, by cladding, in the form of a cylinder around thesurface of a core wire thereby to form a composite magnetic layer.
 17. Amethod for the production of an asymmetric excitation type magneticdevice having a composite magnetic body composed of a plurality ofmagnetic molecules which are different in composition and coercivitywith respect to each other and which are combined so as to have magneticanisotropy oriented in the same direction, wherein, for said compositemagnetic body, a composite magnetic wire having uniaxial anisotropy inan axial direction thereof is formed by subjecting a relatively fineferromagnetic wire to at least one production process such as a twistingprocess thereby to form a composite magnetic body.
 18. In combinationwith an asymmetric excitation type magnetic device having a compositemagnetic body composed of a plurality of magnetic molecules which aredifferent in composition and coercivity with respect to each other andwhich are combined so as to have magnetic anisotropy oriented in thesame direction, a current sensor wherein a predetermined constant biasmagnetic field is normally applied to a magnetic sensor elementconsisting of said composite magnetic body and having uniaxial magneticanisotropy and wherein only a portion of said magnetic sensor elementhaving a low coercive force is magnetized in a positive direction andwhen a negative magnetic force produced by an alternating current to bedetected and which intersects said bias magnetic field is in excess ofsaid bias magnetic field, a pulse signal is generated across a detectingcoil mounted on said magnetic sensor element at a time point when thenext positive magnetic field produced by said alternating current isapplied to and intersects said composite magnetic body.
 19. Anasymmetric excitation type magnetic device having a composite magneticbody composed of a plurality of magnetic molecules which are differentin composition and coercivity with respect to each other and which arecombined so as to have magnetic anisotropy oriented in the samedirection, wherein a detecting coil for producing a detecting magneticfield in a negative or positive direction and a sensor coil for sensinga pulse electromotive force are mounted on said composite magnetic bodywhich is so formed that only a portion thereof having a relatively lowdegree of coercivity is magnetized in a positive or negative directionin response to the direction of the application to said compositemagnetic body of an auxiliary exterior magnetic field such that when anexterior main magnetic field is applied to said composite magnetic bodyand acts in the direction of magnetization of a portion of saidcomposite magnetic body having a high coercivity, the magnetization ofsaid composite magnetic body is reversed at an extremely high speed andsaid auxiliary and main magnetic fields are made to intersect with amagnetic field produced by an electric current to be detected, wherebycurrent sensing is obtained.
 20. An asymmetric excitation type magneticdevice as set forth in claim 19, wherein said electric current to bedetected is made to flow through a cylindrical coil formed by winding asheet-shaped conductor, and wherein said composite magnetic body isarranged in the magnetic field produced at a hollow interior portion ofsaid cylindrical coil.
 21. An asymmetric excitation type magnetic deviceas set forth in claim 19, wherein said electric current to be detectedis made to flow through a spiral conductor and said composite magneticbody is arranged in the magnetic field produced in a hollow interiorportion of said spiral conductor.
 22. An asymmetric excitation typemagnetic device as set forth in claim 19, wherein when the magnetizationdirection of a portion of said composite magnetic body is caused to bevery quickly reversed to produce a pulse electromotive force in saidsensor coil under the application of a combined magnetic filed resultingfrom a plurality of detecting magnetic fields which are graduallyincreased and a magnetic field produced by said electric current to bedetected, the magnitude of said electric current to be detected isdetermined in accordance with a value of said detecting magnetic field.23. An asymmetric excitation type magnetic device as set forth in claim19, wherein the magnitude of said detection magnetic field is sodetermined that when said electric current to be detected reaches apredetermined value of an overcurrent, a pulse electromotive force isgenerated in the sensor coil.
 24. An asymmetric excitation type magneticdevice as set forth in claim 19, wherein pulse electromotive forces dueto noise electric currents discriminated by applying said detectingmagnetic field produced by an alternating electric current to bedetected.
 25. An asymmetric excitation type magnetic device as set forthin claim 19, wherein a switching means for increasing and decreasing thenumber of turns of said detecting coil is provided for determining themagnitude of said detection magnetic field.
 26. An asymmetric excitationtype magnetic device as set forth in claim 19, wherein at least oneferromagnetic control member is disposed in the vicinity of saidcomposite magnetic body and is caused to move toward or away from saidcomposite magnetic body for varying the magnitude of the magnetic fieldproduced by said electric current to be detected.